Three major areas of research are proposed. First, we propose to continue our current synthetic effort in the preparation of new geometric isomers of retinal. New stereo- and regio-selective synthetic routes to the recently isolated hindered isomers (7-cis, 7, 9-dicis, 7, 13-dicis, and 7,9,13-tricis) as well as routes to the hitherto unknown isomers containing the doubly hindered 7, 11-dicis isomers will be pursued. Similar studies to the related vitamin A2 isomers and carotene isomers are also proposed. Secondly, the current effort in the studies of visual pigment analogs will be expanded. The emphasis will be on the preparation of fluorine labelled rhodopsin and porphyropsin analogs. Structural information on the pigment analogs, which should be relevant on the structural properties of the polyene chromophore and the binding site of rhodopsin, will be examined by 19F nuclear magnetic resonance spectroscopy. The method has been successfully applied to many other enzyme systems; but no reports on its successful application to the visual pigments have appeared. Our preliminary results already demonstrated that stable fluorinated rhodopsin analogs can be prepared and in one case the fmr spectrum has been recorded. Other studies on visual pigment analogs include a detailed study of the bleaching intermediates of porphyropsin and its isomers, the search of an infrared sensitive pigment and the possibility to incorporate such retinal analogs into living systems. Thirdly, we propose to continue a detailed study of the photochemistry of polyenes. The emphasis will be on synthetic applications, and correlation of experimental data with theoretical predictions. Specific problems include regio-specific sensitized isomerization of polyenes, the zwitterionic chracter of the excited singlet state of polyenes.